As the often stressful decision deadline for college-bound high school seniors (and their parents) looms across the country, this lite ’n’ leisurely comedy arrives with a well-timed lift to the spirits.

Tina Fey, making her first movie appearance after her critically lauded NBC comedy series “30 Rock” ended its seven-season run in January, stars as an unmarried Princeton University admissions officer just beginning the process of diving into the mountainous pile of applicant folders for the next school year.

Her character, Portia, has a carefully trimmed Bonsai tree on her desk and begins each day spraying her work surface clean with a can of aerosol duster. She’s meticulously organized both in the office and at home—but that’s all about to change.

Paul Rudd plays a much less fastidious director of an “alternative” school with an exceptional student, Jeremiah (newcomer Nat Wolff), whom he’d really like Portia to consider for Princeton. He calls and asks her to come to his New Quest School for a recruitment visit.

It’s that “something more” that drives the movie, as Rudd’s character, John, has reason to suspect his student—an adoptee who was given up by his mother at birth—is actually Portia’s child. He wants to help Jeremiah connect with a Princeton education, certainly, but he also has a bigger connection in mind.

The humor is blended with plenty of heartwarming moments as Fey’s character gradually warms to the maternal instincts she’d been suppressing for so long—but without letting Jeremiah or anyone else know, until close to end of the movie. The running theme of parenthood, be it by nature or nurture, becomes a thread that makes “Admission” more than simply a broader comedy of mismatched—or missing—romantic partners, sight gags and punch lines.

The comedy, though, does comes bopping in from several angles, thanks a cast that includes Lily Tomlin as Portia’s feminist mom, and recurring appearances by Portia’s tweedy professor ex-boyfriend (Michael Sheen) and his stuffy new British lover (Sonya Walger).

The script was based on a 2009 novel of the same name by Jean Haniff Korelitz, a New Jersey resident who married a Princeton prof and who worked a couple of years for the school’s admissions office helping read—and weed—through applications. If “Admission” seems like a movie that gets the right feel of the pressure, emotion and occasional dark joke of the process, that’s why.

Fey, freed now from the weekly responsibilities as creator, executive producer and writer of one of TV’s most successful comedy series, seems like she’s enjoying just going with the easy flow of playing a character, pulling out some dry humor here, bits of snark, snip and sarcasm there, and misty-eyed emotion, righteous indignity or enlightened humility when the plot warrants.

She and Rudd, who appears to be carving out a comfortable niche playing charming nice guys, have an easygoing, unforced chemistry that helps you believe the realistic situation that eventually unfolds with them in the middle of it.

“Admission” can have several meanings. One refers to admittance, as into college; another is about confessing to a mistake or acknowledging a truth; and yet another can be the act of allowing someone close or inside, on an emotional level. The characters in the movie learn about the word in all those shadings.

This modest little movie probably won’t zip to the head of the class as a big hit. But it gets decent marks in my book as a fresh, sharp-witted “dram-edy” with a couple of immensely likeable stars, one that matches its warm springtime humor with a surprisingly tender heart.